Numerical Simulation Of Two-Cavity Flow Scheme Of Vehicle

Supercavitation technology has become a hot topic in drag reduction of underwater vehicles gradually in recent years.Cavitating flow pattern designing is an important part of the hydrodynamic design in supercavitating vehicles.According to the supercavitation theory,four types of cavitating flow can be generated by the underwater vehicle,one of which is the two-cavity flow type.Two-cavity flow type refers to the process that the vehicle is wrapped by two cavities simultaneously,and the head cavity closes above the vehicle with the other one closing in the tail.Due to its unique vacuolar encapsulation,the vehicle has enough wet area to provide lift,but it also reduces drag reduction.For vehicles with low velocity in real motion,it is difficult to generate supercavity to stabilize the vehicle and reduce its drag even using artificial ventilation cavitation technology.Therefore,the application of two-cavity flow pattern is extremely necessary.However,the specific influence between the front and rear cavities is not considered in the application of the two-cavity flow pattern.Therefore,it is urgent to solve the problem that how to design the front and rear cavities rationally to achieve maximum drag reduction.It is of great significance to study the interaction between the front and rear cavities and to find out how to use the two-cavity flow pattern to achieve maximum drag reduction.To solve the above problems in this paper,CFD numerical simulation technology was used to study the conventional symmetric aerated cavitation flow with a rotary body with disk cavitator.And the research was divided into the following two points:1.VOF multiphase flow model and SST turbulence model were used to study the interaction between cavities before and after generation based on two-cavity flow type.Numerical simulation was carried out for the rotary body model of the conventional symmetric cavity with disc cavitator,and the difference of cavities generated between the head disc cavitator and the tail end face under different ventilation rates was obtained,and appropriate ventilation rates were selected respectively for the next numerical simulation.The change of hydrodynamic force and size of the cavity in the whole flow field are discussed when the ventilation sequence,navigation depth and cavitator Angle are changed respectively.2.A dimensionless quantity I was introduced to represent the ratio of the dynamic pressure of the vent on the disc cavitator to the dynamic pressure on the end face of the vent on the disc cavitator.According to the numerical simulation results,the interaction between the head and tail cavities under different ventilation quantities,that is I at different values,was summarized and analyzed.The results show that the head cavity gradually inhibits the expansion of the tail cavity and finally completely engulfs the tail cavity with the increase of I value,Through a lot of numerical simulation,this paper analyzes the interaction between the front and rear cavities and the flow mechanism of the two-cavity flow type,which lays a foundation for further development of the supercavitation technology.